Inkjet printing systems rely on application of a vacuum or negative pressure on the ink supply to help control or prevent drooling of ink at a printhead by causing and maintaining a meniscus in the ink supply line. However, because of air infiltration due to manufacturing defects or other reasons, a significant or sudden increase can sometimes occur in the level of ink and/or associated foam in the supply system. If this ink or foam enters a vacuum supply in communication with the ink supply line, then a catastrophic contamination of the vacuum control system can occur. Such catastrophic failures result in significant downtown time, as well as posing significant costs to restore the vacuum control system. While various attempts have been made at protecting the vacuum control system, significant challenges still remain.